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ANDROID: block/mq-deadline: Only use zone locking if necessary

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Measurements have shown that limiting the queue depth to one for zoned
writes has a significant negative performance impact on zoned UFS devices.
Hence this patch that disables zone locking from the mq-deadline scheduler
for storage controllers that support pipelining zoned writes. This patch is
based on the following assumptions:
- Applications submit write requests to sequential write required zones
  in order.
- It happens infrequently that zoned write requests are reordered by the
  block layer.
- The storage controller does not reorder write requests that have been
  submitted to the same hardware queue. This is the case for UFS: the
  UFSHCI specification requires that UFS controllers process requests in
  order per hardware queue.
- The I/O priority of all pipelined write requests is the same per zone.
- Either no I/O scheduler is used or an I/O scheduler is used that
  submits write requests per zone in LBA order.

If applications submit write requests to sequential write required zones
in order, at least one of the pending requests will succeed. Hence, the
number of retries that is required is at most (number of pending
requests) - 1.

Bug: 264714656
Change-Id: I66265cd86e3f21e1a77ee7e49f94b0e756103c9b
Signed-off-by: Bart Van Assche <bvanassche@google.com>
This commit is contained in:
Bart Van Assche
2023-01-06 17:02:54 -08:00
parent 54678c4c75
commit f57c245b52
2 changed files with 11 additions and 6 deletions
Download Patch File Download Diff File Expand all files Collapse all files

3
block/blk-zoned.c
View File

@@ -519,7 +519,8 @@ static int blk_revalidate_zone_cb(struct blk_zone *zone, unsigned int idx,
break;
case BLK_ZONE_TYPE_SEQWRITE_REQ:
case BLK_ZONE_TYPE_SEQWRITE_PREF:
if (!args->seq_zones_wlock) {
if (!blk_queue_pipeline_zoned_writes(q) &&
!args->seq_zones_wlock) {
args->seq_zones_wlock =
blk_alloc_zone_bitmap(q->node, args->nr_zones);
if (!args->seq_zones_wlock)

14
block/mq-deadline.c
View File

@@ -303,7 +303,8 @@ deadline_fifo_request(struct deadline_data *dd, struct dd_per_prio *per_prio,
return NULL;
rq = rq_entry_fifo(per_prio->fifo_list[data_dir].next);
if (data_dir == DD_READ || !blk_queue_is_zoned(rq->q))
if (data_dir == DD_READ || !blk_queue_is_zoned(rq->q) ||
blk_queue_pipeline_zoned_writes(rq->q))
return rq;
/*
@@ -337,7 +338,8 @@ deadline_next_request(struct deadline_data *dd, struct dd_per_prio *per_prio,
if (!rq)
return NULL;
if (data_dir == DD_READ || !blk_queue_is_zoned(rq->q))
if (data_dir == DD_READ || !blk_queue_is_zoned(rq->q) ||
blk_queue_pipeline_zoned_writes(rq->q))
return rq;
/*
@@ -439,8 +441,9 @@ dispatch_find_request:
}
/*
* For a zoned block device, if we only have writes queued and none of
* them can be dispatched, rq will be NULL.
* For a zoned block device that requires write serialization, if we
* only have writes queued and none of them can be dispatched, rq will
* be NULL.
*/
if (!rq)
return NULL;
@@ -766,7 +769,8 @@ static void dd_finish_request(struct request *rq)
if (rq->elv.priv[0])
dd_count(dd, completed, prio);
if (blk_queue_is_zoned(q)) {
if (blk_queue_is_zoned(rq->q) &&
!blk_queue_pipeline_zoned_writes(q)) {
unsigned long flags;
spin_lock_irqsave(&dd->zone_lock, flags);